Dual single action ram intensifier

ABSTRACT

A ram type intensifier capable of producing a continuous flow of liquid at pressures on the order of 70,000 psi is disclosed, comprised of a pair of alternately and cyclically stroked ram cylinders, in which the flow of pressurized operating fluid to the ram chambers is from a constant pressure source controlled such that simultaneous pressurization of both ram chambers is provided at the end of each cycle so that precompression of the cylinder beginning its pressure stroke is carried out before depressurization of the cylinder ending its pressure stroke. This arrangement prevents pressure variations occurring as a result of the substantial compression of the liquid occurring at these pressure levels.

United States Patent 1191 Mayer July 8, 1975 [54] DUAL SINGLE ACTION RAMINTENSIFIER 3,331,329 7/1967 Bauer 417/342 3,381,833 5/l968 Gordon 60/97E [751 Inventor: 5 9 May", B'mmgham- 3,638,424 2/1972 Valantin 60/371[73] Assignee: The Bendix Corporation, Southfield, PrimaryExaminer-William L. Fleeh Mich. Assistant Examiner-Gregory P. LaPointeFiled y 29 1973 Attorney, Agent, or Firm.|ohn R. Benefiel [2|] Appl.No.: 364,595 [57] ABSTRACT Rented Application Data A ram typeintensifier capable of producing a continu- [63] Continuation-impart ofSer. No 139 098 April 30 l r of liquid at pressures on the Order of70'000 197 abandoned ps1 15 disclosed, comprised of a pair ofalternately and cyclically stroked ram cylinders, in which the flow of52 us. 01 417/346- 60/371 Pressurized Warming fluid the ram chambers is[51] ML F041; l7/0o b 31/02 from a constant pressure source controlledsuch that [58] Field 0 Search 417/225 344447 simultaneous pressurizationof both ram chambers is 417/342, 60/197 371 provided at the end of eachcycle so that precompression of the cylinder beginning its pressurestroke is [56] References Chad carried out before depressurization ofthe cylinder ending its pressure stroke. This arrangement preventsUNITED STATES PATENTS pressure variations occurring as a result of thesub 2,442,916 6/1948 Buchanan 417/346 t j compression of the liquidOccurring at these 2,508,298 5/1950 Saari i i 417/225 pressure levels2,579,670 l2/l95l Hjarpe 417/225 2,858,767 11/1958 Smith 417/346 1Claim, 9 Drawing Figures SHEET EUT L 8 i975 INVENTOR ENDRE A. MAYER BYATTORNEY FFETF? HTML 8 ms SHEET 7?) STdRTuP VALVE M F v w.|||||||/\.l|||

z w p m I I I 0 lull INVENTOR FIG-4 ENDRE A. MAYER ATTORNEY ZliTEUTEMUL81975 3.893.790

SHEET 3 6 202 FIG 5 lNVENTOR ENDRE A. MAYER ATTORNEY 1 DUAL SINGLEACTION RAM INTENSIFIER CROSS REFERENCE TO RELATED APPLICATIONS nowabandoned.

BACKGROUND OF THE INVENTION l. Field of the Invention This inventionconcerns intensifiers and particularly ram type intensifiers capable ofproducing pressures of 70,000-l 00,000 psi.

2. Description of the Prior Art Fluid Jet cutting in which a highpressure liquid jet is used to cut various materials, has long beenproposed and demonstrated experimentally. However, practical industrialapplication of this concept has heretofore been precluded because ofseveral technical difficulties, one of which being the problem ofproviding a suitable source of high pressure liquid.

This is a difficult problem since pressures in excess of 30,000 psi aregenerally required and most such applications would call for pressureson the order of 50-70,000 psi or even higher, and liquid under thesepressures must be supplied continuously in order to yield clean cuts ofthe workpiece.

Furthermore, in many situations the jet assembly must be moved over theworkpiece, such as in automated pattern cutting, and since flexiblehydraulic lines and couplings are not available which are capable ofhandling such pressures, a source which is reasonable in size and weightis highly desirable.

Heretofore, the only commercially available systems for continuouslyproducing a flow of liquid under pressures on this order have beendouble acting differential piston type ram intensifiers, as for examplethat disclosed in US. Pat. No. 2,631,542.

This approach has not been very successful since the deflections tendingto occur at these very high pressure levels are particularly troublesomein this device as three-point" support is involved and the parts must bedesigned to be very large and stiff to prevent binding of the partsduring stroking. Furthermore, the ram tends to be excessively long andbulky since the chambers are arranged end-to-end.

These deflections also tend to aggravate the piston sealing problems andthe heavy construction requires considerable seal servicing effort andconsequent excessive downtime.

A prior art intensifier as described in US. Pat. No. 2,579,670 to Hjarpediscloses a dual free piston intensifier which arrangement wouldalleviate some of the difficulties described above, but the valvingarrangement disclosed in that patent does not provide simultaneouspressurization of the separate cylinders sufficient to precompress theliquid in the cylinder beginning its pressure stroke.

Another prior art intensifier described in US. Pat. No. 3,33 l ,329 toBauer describes such a single acting twin cylinder intensifier whichdoes involve overlap or simultaneous pressurization of both cylinders atthe end of both cylinders at the end of each cycle to alleviate pressuresurges occurring because of the transition conditions existing duringthe changeover of the load from one to the other cylinder. However, asstated therein, this system is designed for pressures in whichcompression of the liquid is negligible. Specifically, the fluid whichoperates the rams is supplied from a constant volume source. This typeof source would not function in the environment of the extremely highpressures causing substantial compression of the working fluid since thecompression of the liquid would create a substantial drop in pressure inthe ram chambers, in turn causing a substantial drop in the outputpressure to thereby defeat the purpose of the overlap.

It has been discovered by the present inventor that a great deal ofcompression of working liquids which are considered incompressible isencountered which would severely hinder the production ofa continuousflow of liquid at these higher pressures with the arrangement describedin the aforementioned patents since compression of the liquid would takeplace for a substantial portion of the pressurization stroke of eachcycle and hence the maximum pressure thereof would not be developedduring this portion of the stroke.

Therefore, it is an object of the present invention to provide anintensifier which is relatively lightweight and compace and yet capableof providing a continuous flow of liquid at pressures on the order of70,000

psi.

SUMMARY OF THE INVENTION This object and others which will becomeapparent upon a reading of the following specification and claims isaccomplished by providing a dual single action ram type intensifierwhich is controlled so that during a portion of each compression strokeof each piston the other piston is fully pressurized to create asubstantial overlap in the operation. The return stroke of each pistonis powered by the working liquid which is supplied thereto undersufficient pressure to minimize the effects of air bubbles on thevolumetric efficiency of the intensifier and on the continuity of flow,as well as to eliminate the need for an arrangement to create returnstrokes thereof by the operating fluid.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic representationof the dual single action ram intensifier arrangement together with itsas sociated valving and hydraulic circuitry.

FIG. 2 is a schematic representation of the dual pistons and theirassociated valving at an intermediate stage of the intensifier cycle.

FIG. 3 is a schematic representation of the dual pistons and theirassociated valving at an advanced state of the intensifier cycle.

FIG. 4 is a schematic representation of the start-up valve and thecontrol valves during initiation of the intensifier operation.

FIG. 5 is a front elevational view of a specific embodiment of the dualpiston intensifier assembly.

FIG. 6 is a view of the intensifier assembly in the direction of thearrow 6-6 in FIG. 5.

FIG. 7 is a view of the section taken along the line 7-7 in FIG. 5.

FIG. 8 is a view of the intensifier in the direction of the arrow 8-8 inFIG. 5.

FIG. 9 is a schematic representation of a second embodiment of the dualsingle action ram intensifier according to the present invention.

DETAILED DESCRIPTION In the following detailed description, certainspecific terminology will be utilized for the sake of clarity and aspecific embodiment described in order to provide a completeunderstanding of the invention, but the invention is not so limited andmay be practiced in a variety of forms and embodiments.

Referring to the Figures and particularly FIG. 1, the intensifier of thepresent invention includes first and second single action ramintensifier means and 12 controlled by a pair of associated pilotpressure operated control valves 14 and 16.

Each ram intensifier cylinder 10 and 12 includes a respective pistonmember 18 and 20 disposed in a respective cylinder means 22, 24. Thepiston members consist of connected large diameter heads 26 and 28 andsmaller diameter heads 30 and 32 which together with the cylinder meansdefine in upper chambers 34, 36 and lower chambers 38 and 40 in thecylinder means 22 and 24.

This arrangement constitutes the basic intensifying apparatus, with alower pressure fluid introduced in each upper chamber 34 and 36 which,acting on the pistons 18 and 20, serves to raise the pressure of aworking liquid introduced to the lower chambers 38 and 40 by virtue ofthe difference in area of the con nected piston heads.

For example, in one design a large diameter head of 2.50 inches diameterand a small diameter head of 0.625 inches diameter was used to create anintensification ratio of 18 to l. Thus, using a 5000 psi supply in theupper chambers, a 70.000 psi pressurization of the working liquid can beobtained.

The supply operating fluid under pressure to each upper chamber isprovided by means of conduits 42, 44 disposed entering the top of eachcylinder 22 and 24 so as to pressurize the volume above each largediameter head 26 and 28.

A source of operating fluid 46 is provided such as a 5000 psi oil pumpwhich may include an accumulator 48, and its communication with theconduits 42, 44 is controlled by the pilot pressure operated controlvalves 14 and 16, respectively.

This source 46 and the associated accumulator 48 must provide a meansfor supplying fluid under pressure to the upper chambers 34 and 36 at asubstantially constant pressure over the range of flow requirementsencountered during the operating cycle. This is particularly importantduring the overlap portion of the cycle to be described in detailherein, since the pressurization of the cylinder upper chamber at thebeginning of its pressure stroke involves a rather rapid increase in thevolume of the upper chamber due to compression of the working fluid.This resulting large momentary flow must be provided by the source 46without causing a substantial pressure drop in the chamber of thecylinder approaching the end of its pressure stroke lest a correspondingdrop in output pressure occur.

Each control valve 14 and 16 includes a valve spool 50, 52 slidablydisposed in a valve bore 54, 56, respectively.

The valve spools 50 and 52 by means of their position in each bore 54,56 control communication between ports 58, 60, and 62, 64 with ports 66,68, respectively, hence providing a three-way function of the valves 14and 16.

Ports S8 and 60 are connected via conduits 70, 72 with the source 46,while ports 62, 64 are connected to the sump 74 via conduits 76, 78, and80. Ports 66 and 68 are connected to the conduits 42 and 44,respectively.

Thus, in the position of the valve spool 50, shown in FIG. 1, the regionof upper chamber 34 of cylinder 22 above the large diameter head isconnected to the sump 74 as port 58 is blocked by the land 82, while inthe position of the valve spool 52 shown therein, the upper chamber 36of cylinder 24 above the large diameter head 28 is connected to thesource 46 as the land 84 blocks the port 64. In the opposite positionsof the valve spools, the opposite would be true. as the land 86 wouldblock the port 62, while the land 88 would block the port 60.

The position of each of the valve spools 50 and 52 in their respectivebores 54 and 56 is controlled by pilot pressures applied to oppositeends 90, 92 and 94, 96 thereof, with these pilot pressures beinggenerated by movement of the pistons 18 and 20 in the cylinders 22 and24. This is accomplished by means of sensing lines 98, 100 and 102, 104communicating with chambers 106, 108, 110, and 112, respectively, eachbeing behind a respective valve spool end 90, 92, 94, and 96.

Sensing line 98 is connected to a sensing port 114 positioned incylinder 22 so that in the full down position of piston 18, it will beuncovered and direct source 46 pressure to chamber 106. Sensing line 100is connected to port 116 positioned in cylinder 24 so that as the piston20 moves downwardly at an intermediate point in its pressurizationtravel, port 116 will be uncovered and direct source pressure to chamber108. Sensing line 102 is connected to sensing port 118 positioned incylinder 22 so that in a similar manner, at an intermediate point in thedownward travel of the piston 18, the port 118 will be uncovered anddirect source pressure to chamber 108. Sensing line 104 is connected tosensing port 120 positioned in cylinder 20 so that at the full downpoint in travel of the piston 28 it likewise is uncovered to directsource pressure to chamber 110.

In order to maintain the spools 50, 52 in the positions created by theapplication of the pilot pressures, mechanical detents 122 and 124 maybe provided. Alternate approaches such as hydraulic lock of the chambers106, 108, 110, and 112 or magnetic detents described infra could beutilized.

in order to insure proper synchronization of the pistons l8 and 20during start up, a start-up valve 126 is provided which serves tomomentarily pressurize conduits 128 and 130 and cause the valve spools50, 52 to be positioned in a manner to be described more complete infra,while normally these conduits are connected to the sump 74 via conduit132 as shown in FIG. 1 and do not affect the operation of the device.

The source 134 of working liquid provides a means for supply of theworking liquid to each of the lower chambers 38 and 40 via conduits 136and 138, check valves 140 and 142, and conduits 144 and 146. For manycutting applications water is preferable as a cut ting fluid and thesystem will be described as such. Since oil is the preferred liquid forhydraulic systems as the intensifier arrangement of the presentinvention, a two-liquid system results. The water is supplied underrelatively high pressure, i.e., 3000 psi for the system described ascontrasted with prior art intensifiers utilizing differing operating andworking fluids for the abovedescribed reason which have supplied theworking fluid under substantially no pressure, and have relied on theoperating fluid to provide the return stroke.

This approach minimizes the effects of bubbles in the working liquidsource 134 on the volumetric efficiency of the system as their volume ismuch reduced initially. In addition, this eliminates the need for aseparate return cycle arrangement with the operating liquid. as the highpressure working liquid provides a means for re- I turning the pistonsto their return position after a pressurization cycle since it forceseach of the pistons upwardly whenever the operating fluid is not appliedto their respective upper chambers 34 and 36.

The working liquid, during the compression stroke of each piston 18, isdirected to a common outlet means comprising the utilization device,such as the fluid jet cutting system 148 described via check valves I50,I52 and conduits I54, I56, and I58. Thus alternating and overlappingpressurization of the cylinders will cause the liquid under highpressure to be directed to the fluid jet cutting system. From thisdescription it can be appreciated that check valves I50 and 152 preventcommunication of the lower chambers 38 and 40 with the common outletmeans except when these chambers are pressurized.

The fluid jet cutting system may include a surge vessel 160 and a nozzle162 of a construction as described in copending application Ser. No.119,758, filed Mar. 1, I971, Nozzle for Producing Fluid Cutting Jet, M.C. Kurko et al.

By reference to FIGS. 2 and 3, the operation of this device after startup may be readily understood. Assuming that the intensifier ispressurized in the manner depicted in FIG. 1, ie. the upper chamber 36of cylinder 24 is pressurized and the upper chamber 34 of cylinder 22connected to the sump, the associated piston 20 will move downwardly,pressurizing the liquid in the lower chamber 40.

when the piston 20 has reached the point intermediate in itspressurization travel depicted in FIG. 2, the sensing port 116 will beuncovered and pressurized by the operating fluid under pressure. Thispressure acting via sensor line 100 in chamber 92 will force valve spool50 to the left as viewed in FIG. 2 to the position depicted therein,which will serve as means to cause pressurization of the upper chamber34 associated with returned piston 18 via conduit 42.

This pressurization will cause the piston 18 to move to compress theworking liquid in the lower chamber 38, while at the same time thepressurization of the upper chamber 36 is maintained substantiallyunabated.

Thus, preceding the return movement of piston 20, both pistons 18 and 20will then be pressurized and move downwardly together (although moreslowly than piston 20 alone) until the piston 20 reaches the pointdepicted in FIG. 3, at which point the sensing port 120 is uncovered.The resulting pressurization of sensor line I04 and connected chamber110 causes the valve spool 52 to shift to the right to the positiondepicted in FIG. 3, which in turn causes chamber 36 to be connected tothe sump 74 and piston 20 to the return position.

In the meantime, piston 18 has descended to the position depicted inFIG. 3 to provide substantially full pressurization and continues todescend, thus maintaining the output pressure.

The amount of overlap is designed so that all compression of the liquid,conduits, etc., has taken place at the beginning of each pressurizationcycle and the pressure of the working liquid compressed by intensifiercylinder I0 has risen to the operating pressure of the device before thedepressurization of intensifier cylinder 12, so that no fluctuations ofthe output flow or pressure is encountered.

It has been determined by the present inventor that the degree ofoverlap necessary at pressures on the order indicated, i.e., 70,000 psi.is considerable since substantial travel of the piston at the beginningof its pressure strike must take place to precompress" the workingliquid in the lower chamber before reducing the pressure in the cylinderending the pressure stroke.

For example. in the system described and with a three-inch stroke, thesensor ports H6 and I20 of intensifier cylinder 12 and H4 and 118 ofintensifier cyl inder It) would be positioned 0.5 inches apart and theresulting compression" travel would be on the order of 1.0 inches inorder to minimize such pressure variations.

Piston 18 then continues downwardly (although more rapidly) until port118 is uncovered causing pressurization of sensor line 104 and chamber112, causing intensifier cylinder 12 to be turned on once again in asimilar manner as with the cycle of piston 20. When piston 18 reachesbottom and port H4 is uncovered, sensor line 98 and chamber 106 arepressurized causing intensifier 10 to be turned off, and piston 8 to bere turned to the return position.

Thus, the cycle repeats itself over and over as long as an operatingfluid is supplied thereto. For the specific system described a cyclerate of 3.65 Hz has been calculated to produce an output flow rate of lgpm at 70,000 psi.

By referring to FIG. 4, the operation of the start-up valve 126 may beunderstood. In the position shown, the start-up valve spool 164 directsvia conduit 166 and port 167 fluid under pressure from source 46 tochambers I68 and 170 of control valves 14 and [6 via port I71, conduits172 and 174. This causes free pistons I76 and 178 to force valve spools50 and 52 into the position shown in FIG. 4 to properly synchronizetheir operation. Valve spool I64 stays in this position only momentarilyuntil pressure builds up in conduit 180 and chamber I82 to cause thevalve spool I64 to move to the right as viewed therein against the biasof a spring 184 to the position shown in FIG. 1. Land 186 then blocksport I67 while land I88 moves to uncover port 190 and place conduits 172and 174 in communication with the sump 74 via branch conduit I92.

The response of the valve spool I64 is controlled by an orifice 194 andaccumulator 196 so that its movement is delayed until the valve spools50 and 52 have shifted. Alternatively, an electronic operator and delayor other arrangements could be used to provide this function.

This arrangement insures that the valve spools are in the properposition at the beginning of operation to initiate the cycling activity.

Also, in connection with start-up, flow into the supply chambers must belimited sufficiently so that too rapid descent of the pistons does notoccur since they encounter relatively little resistance until the outputload builds up, which in turn can cause a loss of of synchronization ifthe return stroke of the piston I8 is not completed before piston 20reaches port 116 and thus initiates a premature power stroke of piston18.

To accomplish this end, flow limiting orifices I98 and 200 can beincorporated in conduits 70, 72 or the associated ports could merely beproperly sized to limit the maximum flow.

Referring to FIGS. -8 a specific hardware embodiment of the presentinvention is depicted.

This includes a pair of intensifier cylinders 202, 204 in side by siderelationship held together by means of a top manifold plate 206,intermediate manifold plate 208, and bottom manifold plate 210, which inturn are held together by sets of studs 212 and 214.

Each intensifier cylinder 202 and 204 includes a control valve assembly216 and 218, while a start-up valve 220 is mounted therebetween.

An accumulator 222 corresponding to the accumulator 48 depictedschematically in FIG. 1 may be mounted between and below the intensifiercylinders 202 and 204, and in communication with conduit 224 andpassages (not shown) in the top manifold plate 206.

FIG. 7 shows intensifier cylinder 204 and its associated control valve218 in section, which is typical of both intensifier cylinders 202 and204. This includes a piston 226 having a large diameter upper head 228s1idably disposed in an upper cylinder 230, connected by a self-aligningcoupling 231 to a smaller diameter lower head 232 passing throughintermediate manifold plate 208 and disposed in a lower cylinder 234.

The upper cylinder 230 includes an outer load bearing sleeve 236 and aninner wear sleeve 238, which has the sensor ports formed therein withthe lower shut-off sensor port 240 shown both which are preferablyshaped as a narrow slit. This form of sensor port reduces seal scuffingand abrasion as the piston 226 tra V verses the inner sleeve 238.

Each sensor port communicates with openings (not shown) in the outersleeve 238 in turn connected to sensor lines 242 and 244.

The piston 228 is cushioned at the top of cylinder 230 by a springwasher stop 246 and at the bottom by a resilient ring 248.

The bottom cylinder 234 includes an outer sleeve 2S0 stretched over aninner sleeve 252 so as to preload the inner sleeve 252 against thepressure loading. This has been found to be an efficient cylinder designfor withstanding very high pressures.

The dynamic sealing of the small diameter head 232 during thecompression stroke is accomplished in this embodiment by means of acontrolled leakage bushing 254. This arrangement, which has beendescribed in the literature, creates a seal under high pressure conditions by creating a pressure differential across the sleeve 2S6.Liquid which gets past the packing 2S8 flows into both clearance 260 andthe space between the small diameter head 232 and the sleeve. Sinceclearance 260 ends in a static packing 262, the liquid is trapped, whileflow past the small diameter head 232 is allowed to escape and becollected by annular slot 264, passage 266 and line 268. Thus, duringthe compression stroke a pressure differential across the sleeve 256 iscreated which causes the sleeve 256 to grip the small diameter headtightly, but during the return stroke to allow free movementtherethrough.

The control valve 218 includes a valve spool 270 slidably disposed in abore 272 and positioned by means of pilot pistons 274, 276, and 278.Valve spool 270 controls the communication of passage 280 and port 281connected with the return line 282 and connected passages 284, 286, and288 and the supply line 224 and connected passage 290, by eitherblocking port 292 or 294 depending on its position in bore 272.

Pilot piston 274 is operated by pressure received from sensor port 240and sensor line 244, pilot piston 276 is operated by pressure receivedvia sensor line 296 connected to the on sensor port of the oppositeintensifier cylinder 202, while piston 278 is operated by pressurereceived via line 298 from the start-up valve 220 (FIG. 6).

A pair of permanent magnets 300, 302 are utilized to provide the detentfunction, holding the valve spool 270 in one position or the other bymagnetic attraction therebetween until overcome by the pilot pistons.

Leakage flow past the pilot pistons 274, 276, and 278 is collected viarelieved areas 304, 306 at each end of the bore 272, and ports 294 and308, and passages 310 and 288, and passed into the return passages 286,284.

In order to collect any leakage flow past the large diameter head 228and from the sensor ports, as well as to allow return flow to fill thespace behind the large diameter head 228 during the return strike, aline 312 communicating with passage 314 in turn communicating withannular passage 316 and opening 318 is provided.

Thus, as the operating fluid is displaced from above the head 228 duringthe return, it may readily flow via port 294, passages 288, 286, 284into line 312 and passages 314, 316, and 318 into the area behind thehead, thus minimizing the resistance during the return stroke.

The working liquid is supplied via line 320 inlet check valve 322, andenters the lower cylinder 234 via passages 324, 326. During thecompression stroke, flow passes into passages 326, 328 past outlet checkvalve 330 into slot 332, passage 340 (FIG. 8) to the output passage 342.The fluid jet cutting nozzle assembly could be threaded directly intothe passage 342 to receive the output flow.

This specific embodiment operates as described in reference to theschematic drawings of FIGS. l5.

In the embodiment described in FIGS. 1-5, sequencing difficulties mayoccur due to unequal pressures generated in the lower chambers from thesame applied pressures in the upper chambers 34 and 36 if significantmanufacturing variations result in differing piston areas, differencesin friction, etc. This difference in lower chamber pressure could causearresting of the motion of the piston approaching the end of itspressure stroke before it has uncovered the final ports 114 or 120.

The alternate embodiment shown in FIG. 9 obviates this potentialdifficulty by modifying the means for generating the shut off signal. inthis embodiment the shutoff signal is generated from ports 344 and 346in cylinders 10 and 12 respectively, these ports being located at alevel such that the pistons 18 or 20 will have carried out theirprecompression at the point at which these ports are uncovered. Theseports 344 and 346 are connected via lines 348 and 350 to chambers 106and 112 of valves 14 and 16 so that the piston which is approaching theend of its cycle is turned off when the other piston has movedsufficiently to uncover its sensing port 344 or 346. Thus, theaforementioned lock up cannot occur, since even if the piston would bearrested in its motion, as the piston starting up reaches full pressuresequencing will proceed since it does not depend on further travel ofthe piston at the end of its stroke.

While specific embodiments have been described, the invention is not tobe so limited and many varia- 9 tions are of course possible within thescope of the present invention.

l claim:

1. A fluid actuated intensifier comprising:

first ram intensifier means including a piston member disposed in acylinder means to form an upper chamber defined by said cylinder meansand one head of said piston and a lower chamber defined by the otherhead of said piston and said cylinder means;

second ram intensifier means including a piston member disposed in acylinder means to form an upper chamber defined by said cylinder meansand one head of said piston and a lower chamber defined by the otherhead of said piston and said cylinder means;

means for introducing fluid into said lower chambers;

means for pressurizing said upper chambers including a constant pressuresource capable of supplying said fluid to said upper chambers without asubstantial drop in pressure due to substantial flow into said upperchambers resulting from compression of said fluid in said lowerchambers;

said means for pressurizing said upper chambers also including controlmeans cyclically pressurizing said upper chambers by communication withsaid constant pressure source so as to cause said piston members toalternately move to pressurize said fluid introduced into said lowerchambers and including means causing each of said pistons to move to areturn position after said pressurization cycle, said control meansfurther including means causing simultaneous pressurization of both ofsaid upper chambers and means causing both piston members tosimultaneously move to pressurize said lower chambers preceding thereturn movement of either of said piston members by said simultaneouspressurization, said control means including a pair of control valvemeans operatively associated with each of said ram intensifiers operableindepen' dently of each other to produce said simultaneouspressurization of said rarn intensifier means. and further includingstart-up valve means causing said control valves to momentarilypressurize one of said upper chambers and depressurize the other of saidupper chambers during start-up of said intensi fier, whereby said pistonmembers initially assume oppositive positions in said cylinder means;

common outlet means receiving fluid pressurized in said lower chambers,including means providing communications of said lower chamber with saidcommon outlet means during said pressurization and discontinuingcommunication during said return movement.

1. A fluid actuated intensifier comprising: first ram intensifier meansincluding a piston member disposed in a cylinder means to form an upperchamber defined by said cylinder means and one head of said piston and alower chamber defined by the other head of said piston and said cylindermeans; second ram intensifier means including a piston member disposedin a cylinder means to form an upper chamber defined by said cylindermeans and one head of said piston and a lower chamber defined by theother head of said piston and said cylinder means; means for introducingfluid into said lower chambers; means for pressurizing said upperchambers including a constant pressure source capable of supplying saidfluid to said upper chambers without a substantial drop in pressure dueto substantial flow into said upper chambers resulting from compressionof said fluid in said lower chambers; said means for pressurizing saidupper chambers also including control means cyclically pressurizing saidupper chambers by communication with said constant pressure source so asto cause said piston members to alternately move to pressurize saidfluid introduced into said lower chambers and including means causingeach of said pistons to move to a return position after saidpressurization cycle, said control means further including means causingsimultaneous pressurization of both of said upper chambers and meanscausing both piston members to simultaneously move to pressurize saidlower chambers preceding the return movement of either of said pistonmembers by said simultaneous pressurization, said control meansincluding a pair of control valve means operatively associated with eachof said ram intensifiers operable independently of each other to producesaid simultaneous pressurization of said ram intensifier means, andfurther including start-up valve means causing said control valves tomomentarily pressurize one of said upper chambers and depressurize theother of said upper chambers during start-up of said intensifier,whereby said piston members initially assume oppositive positions insaid cylinder means; common outlet means receiving fluid pressurized insaid lower chambers, including means providing communications of saidlower chamber with said common outlet means during said pressurizationand discontinuing communication during said return movement.